Shun's younger brother Fuyuki and his girlfriend Mamiya-san kissed.  When Shun finds out, he asks his friends what he should do as Fuyuki's older brother.
Fuyuki ignores his brother and goes on a date with Mamiya.  The gang decides to follow the couple on their date and end up at a karaoke box.
I see you're all doing nothing 
on your day off, as usual.
Veo que no están haciendo nada en su día de descanso como es usual.
Veo que no estáis haciendo nada en vuestro día libre como siempre.
Vocês sem nada para fazer
 no domingo, para variar.